The surface finish becomes important as part of the dielectric at frequencies above 1 gigahertz. The Hall effect becomes more pronounced at high frequencies, and thus the surface resistance is more of a factor in signal loss. Electroless nickel has a much higher loss in Db/cm than HASL. The copper thickness also plays an important role in overall conductivity above 1 ghz. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Kathy Sent: Tuesday, November 29, 2005 5:01 PM To: [log in to unmask] Subject: [TN] I am posting this ? for a colleague: "We are fabricating some boards for a customer that will be 1 oz of copper on Duroid 6010. They are considering two surface finishes: HASL (Hot Air Levelled Solder) and 150u" Nickel under 5-10 u" Gold. The question they are asking is as follows: What are the dielectric properities of the Nickel/Gold finish vs. those of the HASL finish. Does anyone know the answer? I figured that the insulating material (the Duriod) and the conductor thickness (copper) would have the largest influence on dielectric performance and that the surface finish would have a negligible impact on performance. Is this true?" Thanks! --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------